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Related Experiment Videos

Kinematic models and human elbow flexion movements: quantitative analysis.

A W Wiegner1, M M Wierzbicka

  • 1Spinal Cord Injury Service, Brockton/West Roxbury VA Medical Center, Boston, MA.

Experimental Brain Research
|January 1, 1992
PubMed
Summary
This summary is machine-generated.

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Human movement planning prioritizes smoothness. While a minimum-jerk model failed to predict elbow movements, a minimum-snap model accurately described fast movements, suggesting muscle/limb dynamics influence trajectory planning.

Area of Science:

  • Neuroscience
  • Biomechanics
  • Human Motor Control

Background:

  • The central nervous system may plan movements to maximize smoothness, a concept formalized by Hogan's minimum-jerk model.
  • Jerk cost, the integrated mean squared magnitude of jerk, is a key metric for quantifying movement smoothness.

Purpose of the Study:

  • To evaluate the minimum-jerk model's applicability to human one-joint, goal-directed movements.
  • To compare the minimum-jerk and minimum-snap models against experimental kinematic data for movements at various speeds and amplitudes.

Main Methods:

  • Normal subjects performed elbow flexions (5-50 degrees) at self-selected fast and slower speeds.
  • Kinematic parameters and jerk cost were calculated from experimental data and compared with predictions from minimum-jerk and minimum-snap models.

Related Experiment Videos

  • Model boundary conditions were adjusted for non-precise endpoint equilibrium.

    • Main Results:

    • Fast movements (<300 ms) were symmetric; slower movements (>300 ms) were asymmetric with distinct acceleration/deceleration profiles.
    • The minimum-jerk model poorly predicted jerk cost for fast movements.
    • The minimum-snap model (seventh-order polynomial) accurately predicted kinematic parameters for fast movements.
    • Neither model consistently predicted trajectories for slower movements.

    Conclusions:

    • Muscle and limb dynamics likely explain the success of the minimum-snap model in fast movements.
    • Evidence for planning maximal smoothness (minimum-jerk) is lacking in slower human movements.
    • Movement trajectory planning may involve different strategies depending on movement speed.